Hydroprocessing of hydrocarbons

ABSTRACT

A HYDROCARBON HYDROPROCESS WHEREIN THE CHEMICAL CONSUMPTION OF HYDROGEN IS EFFECTED. A COMBINATION PROCESS IN WHICH A HYDROCARBONACEOUS CHARGE STOCK IS REACTED WITH STEAM TO PRODUCE AN EFFLUENT CONTAINING HYDROGEN AND CARBON OXIDES. THE RELATIVELY LOW PRESSURE EFFLUENT IS COMPRESSED TO AN INTERMEDIATE PRESSURE LEVEL, AT WHICH PRESSURE THE HYDROGEN CONCENTRATION IS INCREASED THROUGH THE REMOVAL OF THE OXIDES OF CARBON. THE PURIFIED HYDROGEN STREAM IS THEN COMPRESSED TO A HIGHER PRESSURE LEVEL AND INTRODUCED INTO THE HYDROPROCESSING REACTION ZONE. SPECIFIC HYDROPROCESSES ARE DIRECTED TOWARD THE HYDROGENATION OF AROMATIC NUCLEI, HYDROCRACKING, THE RING-OPENING OF CYCLIC HYDROCARBONS FOR PRODUCING JET FUEL COMPONENTS, DESULFURIZATION, DENITRIFICATION AND HYDROGENATION.

Filed Sept. 24, 1970 (IIIIPII A TTOR/VEYS U.S. Cl. 208-108 5 ClaimsABSTRACT OF THE DISCLOSURE A hydrocarbon hydroprocess wherein thechemical consumption of hydrogen is elected. A combination process inwhich a hydrocarbonaceous charge stock is reacted with steam to producean effluent containing hydrogen and carbon oxides. The relatively lowpressure eluent is compressed to an intermediate pressure level, atwhich pressure the hydrogen concentration is increased through theremoval of the oxides of carbon. The puriied hydrogen stream is thencompressed to a higher pressure level and introduced into thehydroprocessing reaction zone. Specific hydroprocesses are directedtoward the hydrogenation of aromatic nuclei, hydrocracking, thering-opening of cyclic hydrocarbons for producing jet fuel components,desulfurization, denitrification and hydrogenation.

vRELA'F'ED APPLICATIONS The present application is acontinuation-in-part of my copending application, Ser. fNo. 774,378,filed Nov. 8, 1968, now abandoned, all the teachings of which copendingapplication are incorporated herein by specilfic reference thereto.

`APPLICABILITY OF INVENTION The present invention relates to acombination process for effecting hydrocarbon hydroprocessing. Inparticular, the invention is directed toward the catalytic hydrocrackingof heavy hydrocarbonaceous material to produce lower-boiling hydrocarbonproducts. As utilized herein, the term hydroprocessing is intended tobe` synonymous with the term hydrogenatiom and involves the conversionof hydrocarbons at operating conditions which eifect the chemicalconsumption of hydrogen. Processes intended to be encompassed by theterm hydroprocessing, include hydrocracking, aromatic hydrogenation,ring-opening, hydrorefining (for nitrogen removal and olefinsaturation), desulfurization (often included in hydrorening),hydrogenation, etc. One common attribute of these processes, and thereactions being effected therein, is that they are hydrogen-consumingand are, therefore, exothermic in nature. In employing the termhydroprocessing, it is intended to allude to a hydrocarbon conversionprocess wherein there exists the chemical consumption of hydrogen. It isfurther intended to exclude those conversion processes in which thehydrogen consumption stems primarily from the saturation of lightolelins, resulting from undesirable cracking of charge stock and/ orproduct component, which produces light gaseous waste material,principally methane, ethane and propane. In the interest of brevity, thefollowing discussion will be limited to that hydrogen-consuming processcommonly referred to as catalytic hydrocracking.

Hydrocracking is primarily employed for the purpose of converting arelatively heavy hydrocarbonaceous charge stock into lower-boilinghydrocarbon products. For example, a heavy vacuum gas oil may beintended for conversion into lubricating oil, kerosene, gasoline boilingrange naphthas, or a product slate comprising a arent O ice mixturethereof. Hydrocracking involves cracking of high molecular weightmaterials followed by hydrogenation of thehcracked products in order toproduce a substantially saturated product stream. A hydrogen atmosphereof relatively high purity is a requirement for effecting hydrogenationreactions, particularly hydrocracking, and there is a corresponding needto produce hydrogen of the requisite purity from various externalsources. With respect to many of the hydrogen-consuming processes, aspecial unit is designed and constructed for the sole purpose ofproducing -high purity hydrogen which is then introduced into thehydrocarbon hydroprocess.

External hydrogen, to be utilized in a hydrogen-consuming process, maybe obtained, for example, from either a catalytic reforming process, ora hydrogen-producing unit, and either directly, or from storage at arelatively low pressure. Make-up hydrogen, to compensate for thatchemically consumed wtihin the hydroprocess, is compressed to therequired pressure and introduced into the hydroprocessing reaction zone.Recently, however, hydroprocessing reactions, and, in particular,hydrocracking reactions, have been elfected at exceedingly highpressures up to about 10,000 p.s.i.g. Hydrocracking reactions, forexample, are effected at pressures in the range of about 1,000 to about5,000 p.s.i.g., and preferably at pressures in the range of about 1,500to about 3,000 p.s.i.g. For reasons well within the purview of thosepossessingA expertise in the art, reciprocating or piston-typecompressors have been employed to compress the hydrogen stream to theextent necessary to achieve the requisite reaction zone pressure. Ingeneral, as the size of the processing unit increases, resulting inincreased ow rates, the single-train centrifugal compressor system isdesirably installed. Those skilled in the art are also aware thatreciprocating, or piston-type compressors have unusually highmaintenance factors, are cumbersome and generally require closesupervision for proper operation. Therefore, it is highly desirable toprovide a process for the hydroprocessing of the make-up hydrogen streamin a relatively simple and economical manner.

With respect to a centrifugal compressor system, a major considerationin the determination of a practical installation is the inlet cubic feetper minute (c.f.m.) to the last impeller in the train. While someimpellers have been furnished with capacities in the 350 to 450 c.f.m.range a't peak efficiency, a more realistic capacity is 500 c.f.m., fora present-day centrifugal compressor, and driver speeds of |10,000 to13,500 r.p.m. In an all centrifugal compressor unit, this results in ahorsepower requirement in the 20,000 to 25,000 range for the feed gasand 5,000 to 7,500 for the recycle gas. Due to considerations of processand process stability, the recycle is incorporated in a separate casing,although it may be used alternatively as a combination feed gas boosterand recycle unit. Wiht the lower molecular weight gas, accompanied bythe high pressure head required, the number of centrifugal compressorcasings becomes a serious consideration. Notwithstanding advancedtechnology in turbo-machinery, centrifugal compressors have not beenfound 'suitable for this use due to the inabiilty to design anacceptable machine at an eco- Inomic cost to accomplish the desiredresult.

OBJECTS AND EMBODIMENTS Accordingly, it is an object of my invention toprovide a process for the conversion of hydrocarbons. A corollaryobjective is to afford a hydrocarbon hydroprocess wherein the chemicalconsumption of hydrogen is effected. Another object of this invention isto provide a method for effecting the hydrocracking of heavyhydrocarbonaceous material. A specific object is to afford an improvedmethod for producing high purity hydrogen for use in a hydrocrackingprocess.

Therefore, in accordance with one embodiment of this invention, there isprovided a method for the hydrogenation of hydrocarbons which comprises:

(a) Introducing feed hydrocarbons to be hydrogenated into a firstreaction zone maintained under hydrogenation conditions including thepresence of hereinafter specified hydrogen gas and a pressure from 1,000p.s.i.g. to 5,000 p.s.1.g.;

(b) Separating the efuent from said first reaction zone into a hydrogenstream suitable for recycle to said first zone, a normally gaseoushydrocarbon stream and a normally liquid hydrocarbon stream;

(c) Introducing added hydrocarbons to a second reaction zone maintainedunder conditions including a relatively low pressure from 100 to 400p.s.i.g. and sufiicient to convert said introduced gaseous hydrocarbonsinto a mixture of hydrogen and carbon oxides;

(d) Compressing said mixture of hydrogen and carbon oxide to arelatively high pressure from 1,000 p.s.i.g. to 5,000 p.s.i.g.;

(e) Passing said compressed mixture into a separation zone underconditions sufficient to produce a hydrogen product stream at a pressurefrom 1,000 p.s.i.g. to 5,000 p.s.i.g. and a carbon oxide product stream;

(f) Introducing said hydrogen product stream into said first reactionzone as the specified hydrogen gas; and,

(g) Recovering said normally liquid hydrocarbon stream.

In another embodiment, my invention involves a hydrocarbon hydroprocesswhich comprises the steps of (a) Reacting a first hydrocarbonaceouscharge stock and hydrogen in a first reaction zone, at conditionsselected to effect the chemical consumption of hydrogen including anelevated pressure from 1,000 to about 5,000 p.s.i.g.;

(b) Separating the resulting first zone efiiuent to provide a firsthydrogen-rich principally vaporous phase and a first normally liquidphase;

(c) Separating said first liquid phase to provide a second principallyvaporous phase and to recover a second normally liquid phase;

(d) Reacting a second hydrocarbonaceous charge stock and steam in asecond reaction zone at a pressure of 100 to about 4000 p.s.ig. and at atemperature selected to produce an effluent containing hydrogen andoxides of carbon;

(e) Centrifugally compressing at least a portion of the resulting secondreaction zone effluent to a pressure from 500 to about 3,000 p.s.i.g.;

(f) Removing oxides of carbon from said compressed second reaction zoneefiiuent to produce a purified hydrogen stream;

(g) Compressing said purified hydrogen stream to a pressure of 1,100 toabout 5,100 p.s.i.g.; and

(h) Introducing the thus-compressed purified hydrogen stream into saidfirst reaction zone.

In still another embodiment, this invention includes the methodhereinabove described wherein said conditions are hydrocrackingconditions and said high pressure is obtained by passing said mixturethrough a multiple-stage centrifugal compressor.

In essence, therefore, the present invention provides an improved methodfor the hydrogenation of hydrocarbons utilizing a specified hydrogenstream which is obtained from a specific hydrogen-producing plant. In apreferred embodiment, the hydrogen-producing plant is a steam reformingunit which utilizes centrifugal compression between conversion zones andthe carbon dioxide adsorption zones of the unit.

Other embodiments, as hereinafter set forth in greater detail, areprincipally concerned with particularly preferred processing techniquesand ranges of various process variables. These, as Well as other objectsrelating to the present inventive concept, will become evident from thefollowing additional description of the process. In one such otherembodiment, the second hydrocarbonaceous charge stock comprises at leasta portion of said second vaporous phase.

SUMMARY -OF INVENTION Various methods of producing hydrogen are wellknown to those skilled in the art. For example, U.S. Pat. No. 2,750,261,Ipatieff, et al., teaches a process for the production of hydrogenthrough the inter-action of an aliphatic hydrocarbon and steam atelevated temperatures, and in the presence of a catalytic material. Asnoted from the stoichiometry presented in this patent, hydrogen andcarbon dioxide are the products from the steam cracking of a normallygaseous hydrocarbon. As currently practiced, hydrogen production in thismanner involves the major processing steps of steam reforming, water-gasshift relaction and the removal of acid gases. It is known that varioushydrocarbonaceous materials may be employed as feed streams to the steamreforming reaction zone. It is generally acknowledged that the idealfeed stream is rich in low molecular weight, normally gaseous paraffinsincluding methane, ethane, and propane, with natural gases of relativelylow nitrogen content being distinctly preferred.

In the production of hydrogen, in accordance with the steam reformingprocess, preheated feed gases and superheated steam are introduced intocatalyst-filled tubes in the furnace-type reforming zone at atemperature of about 1400L7 F. to about 1500 F., the hydrocarbons reactwith steam to form hydrogen and carbon oxides. The initial reaction maybe represented by the following formula:

The carbon monoxide which is formed is then reacted with excess steamoriginally present in the feed mixture to form additional hydrogen viathe following reaction:

This latter reaction is known as the water-gas shift reaction. Finally,the remaining impurities, such as carbon monoxide, are converted into amore desirable hydro carbon by reaction with hydrogen. Typically, amethanator is employed to remove carbon monoxide to extremely lowlevels. This latter reaction is promoted by a nickel catalyst at atemperature of about 500 F. to about 800 F. in accordance with thefollowing reaction:

Alternatively, a nitrogen washing column may be employed to removemethane and carbon monoxide, thereby producing a gas suitable for thesynthesis of ammonia.

Operating conditions for the production of hydrogen include a steam tocarbon ratio from about 1.l:6.0, relatively low pressures from p.s.i.g.to about 400 p.s.i.g. and a catalytic composite comprising nickel.Temperatures, as previously mentioned, will generally be within therange from l400 F. to 1500" F. Space velocities are based on methaneequivalents per hour per volume of catalyst, and will typically rangebetween 50 and 1,000.

Generally, the stream produced from the steam reforming operations willcontain from 80.0% to 98.0%, on a mole basis, of hydrogen. Puritiesabove or below these limits can be produced by those skilled in the artaccording to the needs of the process Where the hydrogen is to beutilized. In some cases it is possible to produce hydrogen in a purityexceeding 98.0%, but rarely will this be a requirement for ahydrogen-consuming process. In the practice of the present invention, itis preferred that the hydrogen produced be at least 80.0% pure.

Therefore, according to the description of the present invention thusfar presented, a steam reformer, water-gas shift converter and in aacid-gas removal system are combined in an economical manner utilizingcompression between the Water-gas shift converter and the acid-gas removal system to produce relatively high purity hydrogen for use in ahydrogen-consuming process. The acid-gas removal system referred toherein may comprise conventional methods for carbon dioxide removalincluding mono-ethanolamine (MEA) adsorption, hot potassium componentadsorption, methanol wash, etc. In a preferred embodiment of thisinvention, the CO2 adsorption system will utilize the conventional amineadsorber including conventional solvent regeneration facilities.Furthermore, the hydrogen eiiluent gas from the CO2 adsorption systemmay be passed directly into the hydrogenation reaction zone, or may bepassed into a methanation reaction zone, as previously described, andthen into the hydrogenation reaction zone. The present invention isintended to encompass the methanation reaction as an integral part inthe overall process; however, it is understood, if desired, thatmethanation can be omitted without departing from the spirit and intentof the'inventive concepts set forth herein.

The centrifugal compressors referred to herein are conventional, and maybe obtained from any number of manufacturers including Clark, Elliot,Ingersol-Rand, etc. These machines are multi-stage in employing asuccession of pressure increasing impellers as well as in accommodatingimpeller series in each of the successive case stages and arecustomarily connected in tandem to a common drive shaft which isconnected to a common `driver and gear speed changer if required. Thepresent invention is specifically directed to the use of multiple-casestage centrifu-gal compressors Iwhich significantly increase thepressure of the produced hydrogen stream containing from 10.0% to 30.0%carbon dioxide, at a point prior to the conventional carbon dioxideladsorption zone ina hydrogen-producing plant. As hereinafter set forthin greater detail, one scheme involves increasing the pressure of theCO2-containing hydrogen stream, followed by `CO2 removal which, in turn,is followed by additional compression to the level required in thehydroprocessing reaction zone.

As hereinbefore set forth, the present invention is specicallyapplicable to a hydrocracking process, although it is not intended thatthis invention be unduly limited thereto. It is known in the art thathydrocracking, or destructive hydrogenation, eects definite molecularchanges in the structure of hydrocarbons. Such a reaction producesrelatively light, or lower molecular weight hydrocarbon products from Iarelatively heavy hydrocarbon feed stock, and is particularly applicableto producing products within the gasoline boiling range. For example, ahydrocracking process can convert a petroleum feed stock, such as a gasoil, virtually, completely into gasoline boiling range products. Ineffect, the reaction zone efuent contains unreacted hydrogen, normallygaseous hydrocarbons and normally liquid hydrocarbons. 'Ihe normallyliquid hydrocarbons are generally recovered by fractionation intovarious boiling range cuts according to the desired product slate.Therefore, hydrocracking may be designated as a conversion processwherein lower molecular Weight products are produced, which products aresubstantially more saturated than when hydrogen, or a hydrogen-donormaterial is not present.

Although many of the prior art processes are conducted on a strictlythermal basis, the preferred processing technique of the presentinvention involves the utilization of a catalytic composite employed ina fixed-bed system. Through the judicious selection of catalyst, thehydrocracking reaction can selectively convert a wide variety of feedstocks into lower-boiling distillates with significantly less coke andlight gas yield than is usually produced by conventional catalyticcracking processes conducted in the substantial absence of hydrogen. Asused herein, the term hydrogenation is intended to allude broadly to theaddition of hydrogen to unsaturated bonds between two atoms. Therefore,the process to which invention is applicable is suitable for any processinvolving the contacting of hydrogen and normally liquid hydrocarbons atreaction conditions selected to effect the chemical consumption ofhydrogen. The particular operating conditions for the varioushydrogen-consuming reaction and processes are well known to thoseskilled in the art. For example, the desulfurization of lubricating oilsboiling between about 400 F. and 800 F., is effected at temperaturesranging from 500 F. to about 1,000 F. and pressures up to about 10,000p.s.i.g. Liquid hourly space velocities may be varied from 0.1 to about20.0. Those skilled in the art are familiar with these operatingconditions and are capable of selecting the proper conditions inaccordance with the characteristics of the particular system inquestion.

As hereinbefore stated, with respect to the hydrocracking process,relatively heavy hydrocarbonaceous material is converted intolower-boiling hydrocarbon products. The normally liquid hydrocarbonstream, separated from the eilluent emanating from the hydrocrackingreaction zone, can further be separated into desired fractions such as agasoline fraction containing butanes and other hydrocarbons boiling upto about 400 F., a middle-distillate oil containing hydrocarbons boilingfrom about 400 F. to about 650 F., a heavy hydrocarbon fraction boilingfrom about 650 F. to about 950 F., and or a recycle oil containing thosehydrocarbons boiling above a temperature of about 950 F. `Otherfractions can, `of course, be separated as desired. As hereinafter morefully discussed, at least a portion of the separated light hydrocarbons,including normally gaseous hydrocarbons, may be introduced as a part ofthe feed mix-ture to the steam reforming zone for the production ofhydrogen. In some instances,I that portion of the normally liquidproduct efliuent boiling above the end point of the ultimately desiredproduct, will be recycled to combine with the charge stock to thehydrocracking reaction zone. In such situations, the combined liquidfeed ratio to the hydrocracking reaction zone will be in the range ofabout 1.1 to about 6.0.

In the hydrocracking process, the hydrocarbons to be converted intolower-boiling material are contacted With a suitable catalyst at atemperature from 450 F. to about 900 F. and under an imposed pressurewithin the range of 1000 p.s.i.g. to about 5000 p.s.i.g., a liquidhourly space velocity from 0.1 to about 10.0 and in the presence ofhydrogen in amount of about 1,000 to about 30,000 s.c.f./ bbl. Thehydrocracking conditions are chosen to produce an eluent streamcontaining unreacted hydrogen, normally gaseous hydrocarbons andnormally liquid hydrocarbons.

It is distinctly preferred that the pressure imposed upon thehydrocracking reaction zone be at least 1,000 p.s.i.g., and still morepreferable for the pressure to be within the range of about 1,500 toabout 3,000 p.s.i.g. i.e. 2,000 to 2,500 p.s.i.g. At pressures belowabout 1,500 p.s.i.g., the recycle oil obtained from the hydrocrackingreaction is dehydrogenated as evidenced by an increased Ramsbottornresidue as compared to the charge, whereas pressures above 1,000p.s.i.g., preferably above 1,500 p.s.i.g., the recycle oil from thehydrocracking operation has a reduced Ramsbottom carbon, and, therefore,:can be effectively recycled to extinction.

The feed stocks which may be satisfactorily converted in the presentinvention have a. wide range of compositions, and may contain largeconcentrations of saturates and aromatic hydrocarbons. In thehydrocracking reaction, saturates are cracked to gasoline boiling rangeparafnic hydrocarbons containing a greater than equilibriumconcentration of isoparains in the product effluent. In the case ofpoly-nuclear aromatics, these are partially hydrogenated with thehydrogenated ring portion being cracked to afford alkyl-substitutedbenzene and an isoparain. Most generally, for the hydrocrackingreaction, the charge stock will nange from naphtha land kerosene throughthe light and heavy gas oils. A particularly suitable feed stock will beone containing paraflinic hydrocarbons of at least 5 carbon atoms permolecule and having an upper boiling point in the range of from 600 F.to about 1100 F.

Product yields from the process of the present invention are dependentupon the nature of the charge stock, process conditions, availability ofhydrogen and the catalytic composite employed. It should be noted,however, that the operating conditions and the specific catalystemployed form no essential part of the present invention except withinthe concepts described herein. The catalyst employed may be selectedfrom the various well known hydrocracking catalysts which generallycomprise a metallic hydrogenation component and a solid acidichydrocracking component. Preferably, the hydrocracking catalyst furthercomprises a minor amount of an activitycontrolling material whicheffectively provides a balance in the catalyst-hydrogenation activityrelatively to the acidity during the overall conversion reaction. Thecatalyst so constituted serves a dual function; that is, it isnon-sensitive to the presence of substantial quantities of nitrogenousand sulfurous compounds, while at the same time is capable of effectingthe destructive removal thereof, and also of converting at least aportion of those hydrocarbons boiling in the upper range of thefeedstock; in excess of about 600 F. to about 700 F.

Suitable catalytic composites comprise at least one metallic componentselected from the metals of Groups VI-B and VIII of ther Periodic Tablecombined with a suitable refractory inorganic oxide such as alumina,silica, and mixtures thereof. It is preferred that the catalyst compriseat least two refractory inorganic oxides, and preferably alumina andsilica. When employed in such a combination, the silica will be presentin an amount within the range of about 10.0% to about 90.0% by weight.The alumina-carrier material may be amorphous or zeolitic in nature, thelatter often being referred to as crystalline aluminosilicate. 'Ihetotal quantity of metallic cornponents within the catalytic compositedisposed within the hydrocracking reaction zone is generally within therange of from about 0.1% to about 20.0% by weight. The Group VI-B metal,such as chromium, molybdenum or tungsten, is usually present in lanamount of from about 0.5% to about 10.0% by weight. The group VIIImetals, which may be divided into two sub-groups, are present in anamount of from about 0.1% to about 10.0% by weight. When an iron groupmetal such as iron, cobalt or nickel is employed, it is present in anamount from about 0.2% to about 10.0% by weight. While, if a noblemetal, such as platinum, palladium, iridium, osmium, ruthenium, orrhodium, is employed, it is present within an amount within the range ofabout 0.1% to about 4.0% by weight. A preferred catalytic composite, forutilization in the present process, comprises nickel in an amount fromabout 0.5% to about 10.0% by weight, composited with an alumina-silicacarrier material. A preferred carrier material constitutes faujasite, aform of crystalline aluminosilicate, which carrier material is at leastabout 90.0% by weight zeolitic. The catalytic composite may bemanufactured in any suitable manner known to those skilled in the art.Thus, where the catalyst contains nickel, the method of preparationgenerally involves rst forming an aqueous solution of a watersolublecompound such as nickel nitrate hexahydrate. The alumina particlesserving as a carrier material are cornmingled with the aforementionedaqueous solution and subsequently dried at a temperature of about 200 F.The dried composite is then oxidized in an oxidizing atmosphere such asair, at an elevated temperature from 1100 F. to about 1700 F., and for aperiod of from 2 to about 8 hours. The exact manner of formulating thecatalytic composite is not critical, and is well known to those skilledin the art, and only general reference thereto need be made herein.

Since hydrogen is consumed within the hydrocracking reaction zone, it isnecessary to maintain an excess of hydrogen therein. The presentinvention utilizes a steam reforming reaction zone in order to obtainthe hydrogen necessary to supplant that chemically consumed within theprocess. For the production of hydrogen in accordance with thisinvention, various feed stocks may be satisfactorily used. It isdistinctly preferred, however, that at least one of the feed stocksencompass normally gaseous hydrocarbons of the type found inconventional natural gas streams. It is further preferred that the feedstock have a relatively low nitrogen content. In one embodiment of thepresent invention, the normally gaseous hydrocarbons separated from theeuent of the hydrocracking reaction zone, are introduced into the steamreforming reaction zone, and may be so introduced in admixture with thefeed stream from a suitable external source. Other feed stocks may beused in and of themselves, or combination with each of theabove-mentioned feed stocks, or in combination only with the natural gasfeed stock. Such other hydrocarbons may be ethylene, ethane, propane,propylene, hexene, hexane, normal heptene, etc., mixtures thereofincluding various petroleum derived fractions, such as light naphtha,heavy naphtha, gas oil, as well as mineral oils, crude petroleum, toppedresidual oil, refinery and coke oven gases. A light naphtha generallyhas a boiling range from about 100 F. to about 250 F., while a heavynaphtha boils from about 200 F. to about 400 F., and a gas oil indicatesa boiling range from about 400 F. to about 700 F. As utilized herein,the term added hydrocarbons, or words of similar import, is intended toallude to the fact that the charge stock to the steam reforming reactionzone may be obtained from an additional, or extraneous source other thanthe process encompassed by the series of interrelated andinter-dependent steps making up the present invention.

In view of the fact that high purity hydrogen has a relatively lowmolecular weight, centrifugal compressors have not been consideredfeasible or economical in compressing the hydrogen to the required highpressure level. The carbon dioxide-containing hydrogen stream has ahigher molecular weight and can, therefore, be centrifugally compressedto the elevated pressured level. The corresponding increase in powerrequirements when compressing the carbon dioxide-containing hydrogenstream, presents a problem with respect to the economics of the process.On one hand there exists the desirability of using centrifugalcompressors, and the other an increase in utility costs. By optimizingthe degree to which the pressure of the carbon dioxide/hydrogen streamis raised, followed by carbon dioxide removal and further compression tothe desired pressure level, the overall economics can be improved. Thus,where the pressure is in the range of 1,500 to about 3,000 p.s.i.g., thecarbon dioxide-containing hydrogen stream is centrifugally compressed toa pressure level from about 1,200 to about 2,000 p.s.i.g., and thepurified hydrogen stream, after carbon dioxide removal is furthercompressed to a pressure from 1,600 to about 3,100 p.s.i.g. This permitsthe second compression to be effected either with a centrifugalcompressor, or a reciprocating compressor. This particular embodiment ofmy invention is that which is illustrated in the accompanying drawing.

DESCRIPTION OF DRAWING The present invention may be more clearlyunderstood upon reference to the accompanying drawing, wherein oneembodiment is illustrated. In the drawing, various heaters, coolers,control valves, start-up lines, instrumentation and other miscellaneousappurtenances have been reduced in number, or eliminated entirely, asnot being necessary for the purpose of illustration. Such modificationsare well within the purview of those possessing ordinary skill in theart.

Referring now to the drawing, a heavy hydrocarbonaceous charge stock,boiling between 400 F. to about 1,000 F., is introduced into the processby way of line 21 wherein it is admixed with a puried hydrogen stream inline 17 and a recycle hydrogen stream from line 25.

In many instances, the hydrocarbonaceous charge stock will also beadmixed with a heavy hydrocarbon recycle stream from line 30. Themixture continues through line 21 into reactor 22 which constitutes acatalytic hydrocracking reaction zone. Illustratively, the operatingconditions maintained in reactor 22 include a temperature of about 700F., a liquid hourly space velocity of about 0.75 and a pressure of about2,000 p.s.i.g. These conditions are sufficient to produce an efuentstream containing normally liquid hydrocracked products; that is, aliquid product stream being lower boiling than the fresh feed chargestock, a hydrogen-containing stream and a normally gaseous hydrocarbonfraction comprising low molecular weight paranic hydrocarbons includingmethane, ethane and propane. The effluent from reactor 22 is withdrawnthrough line 23 into cold separator 24 which functions at substantiallythe same pressure but at a temperature in the range of about 60 F. toabout 140 F. Hydrogen lgas of relatively high purity is separated fromthe effluent in separator 24 and recycled via line 2.5 to reactor 22.The remainder of the hydrocracked product effluent is withdrawn throughline 26, and introduced thereby into separation zone 27. Suitabledistillation conditions are maintained in separation zone 27 in order toproduce an overhead fraction comprising light hydrocarbons, which arewithdrawn via line 28, and a distillate fraction, for example, boilingwithin the gasoline boiling range which is removed via line 29. Also, ashereinabove set forth, a residue stream comprising heavier hydrocarbonsis withdrawn via line 30 and preferably recycled therethrough tohydrocracking reaction zone 22.

Referring now to the hydrogen-producing section of the present process,a natural gas stream is introduced into the process by way of line 1.The natural gas stream has the composition indicated in the followingTable I:

TABLE I Natural gas composition In the illustrated embodiment, a portionof the light paraffinic hydrocarbons from line 28 is diverted by way ofline 2 being admixed with the natural gas in line 1. This feed mixtureis introduced into treating zone 3 which comprises a series of zincoxide catalyst beds for the purpose of removing sulfur from the gaseousfeed streams. The treater functions at a temperature of about 750 F. inaccordance with practices well known to those skilled in the art. If twocatalytic vessels are employed in series for treating zone 3, whensulfur breaks down in the first vessel it is taken out of service andrecharged with fresh zinc oxide. The freshly charged vessel is thenpreferably placed in service in the downstream position. Treater 3 isoperated under conditions sufficient to reduce the total sulfur contentof the feed gas to less than about 0.5 p.p.m. The treated gas passes outof treating zone 3 through line 4, is admixed with steam in line 5 andpasses therethrough into reforming zone 6.

Reforming zone 6 contains a series of vertical tubes filled with anickel catalyst, and the gas stream mixture reaches reformer 6 at atemperature of 1541 F. and a pressure of about 250 p.s.i.g. The efliuentgas in line 7 has the following composition on a dry basis: 1.81 vol.percent methane, 11.20 vol. percent carbon dioxide, 11.64 vol. percentcarbon monoxide, 75.30 vol. percent hydrogen, and about 0.05 vol.percent nitrogen.

The carbon monoxide contained in the reforming furnace efuent in line 7is converted into carbon dioxide and additional hydrogen in converter 8which comprises two shift converters. The first shift converter operateswith an inlet temperature of 275 F. and an outlet temperature of about772 F. The second shift converter functions with an inlet temperature ofabout 394 F. and an outlet temperature of 425 F. The gas is cooledbetween the two shift converters by heat-exchange means, notillustrated, generally with boiler feed water employed in the productionof steam.

The composition of the gas stream after each of the two shift convertersin converter zone 8, on a dry basis, is presented in the following TableII:

TABLE II.-SHIFT CONVERTER STREAM COMPOSITIONS Volume percent The eluentstream, containing about 20.0 vol. percent carbon dioxide, is withdrawnvia line 9 and passed into centrifugal compression zone 10, which, aspreviously indicated, comprises a series of case stages individuallycontaining their respective impeller series. In passing throughcompressor 10, the hydrogen/carbon dioxide is progressively increased inpressure to a level of about 1,600 p.s.i.g. The compressor discharges byway of line 11 into a conventional carbon dioxide adsorber 12 of themono-ethanolamine type. Adsorber 12 is operated in accordance withconventional techniques involving the the introduction of the compressedgas into the lower end of the adsorbent column, which gas then flowsupwardly through the suitable liquid contact devices against downflowingliquid mono-ethanolamine being introduced -by way of line 13. The richmono-ethanolamine, having a high carbon dioxide content, is withdrawn byway of line 1S and passed into a conventional stripping regenerationsystem for the recovery and reuse of the mono-ethanolamine solvent.

The carbon dioxide content of the gas is reduced from 20.24 vol. percentto less than 180 p.p.m. The gas, in line 14, is then generally scrubbedwith a small amount of process condensate, not illustrated, in order toremove the last traces of mono-ethanolamine. However, since the washingcondensate is also saturated with carbon dioxide in some cases, thecarbon dioxide content of the gas in line 14 increases to 242 p.p.m.;the gas has the composition indicated in Table III:

TABLE III The purified hydrogen stream emanates from adsorber 12 at apressure of about 1,550 p.s.i.g., and is introduced by way of line 14into centrifugal compressor 16 wherein the pressure is increased to alevel of about 2,100 p.s.i.g. In a preferred embodiment of thisinvention, the purified hydrogen gas in line 17 is now preheated bymeans not shown, and passed via line 18 into methanator 19. Methanator19 contains a nickel catalyst and converts residual carbon monoxide andcarbon dioxide to methane. The gas reaches methanator 19 at atemperature of about 700 F. and a pressure of about 2,050 p.s.i.g., andhas the following composition: 2.44 vol. percent methane, 97.50 vol.percent hydrogen, 0.06 vol. percent nitrogen and less than about p.p.m.carbon oxides. The gas stream emanating from methanator 19 passesthrough line 20 into line 17. If desired, a selected amount or, in fact,all of the gas in line 17 may be introduced into the hydrocrackingreaction system. The puritie'd gas in line 17 is now passed at apressure of about 2,000 p.s.i.g., in admixture with the fresh feedcharge stock in line 21, into reactor 22.

It can be seen that the present invention provides a method forhydrogenating hydrocarbons in the presence of relatively high purityhydrogen, wherein the hydrogen employed in the hydrogenation reaction isproduced at the required pressure by centrifugal compression in a steamreforming operation. This interrelated and interdependent series ofprocessing steps accomplishes a hydrogenation reaction, and, inparticular, a hydrocracking reaction in a facile and economical manner.

I claim as my invention:

1. A hydrocracking process which comprises the steps of:

(a) reacting a first hydrocarbonaceous charge stock and hydrogen, in aiirst reaction zone, at conditions selected to effect the chemicalconsumption of hydrogen, including an elevated pressure from 1,500 toabout 3,000 p.s.i.g.;

(b) separating the resulting rst zone eiuent to provide a firsthydrogen-rich principally vaporous phase and a rst normally liquidphase;

(c) separating said iirst liquid phase to provide a second principallyvaporous phase and to recover a second normally liquid phase;

(d) reacting a second hydrocarbonaceous charge stock comprising at leasta portion of said second vaporous phase and steam, in a second reactionzone, at a pressure of 100 to about 400 p.s.i.g. and at a temperatureselected to produce an eluent containing hydrogen and oxides of carbon;

(e) centrifugally compressing at least a portion of the resulting secondreaction zone eliiuent to a pressure from 1,200 to about 2,000 p.s.i.g.;

12 (f) removing oxides of carbon from said compressed second reactionZone effluent to produce a hydrogen stream;

(g) compressing gas consisting essentially of said puried hydrogenstream to a pressure of 1,600 to about 3,100 p.s.i.g.; and,

(h) introducing the thus-compressed purified hydrogen stream into saidrst reaction zone.

2. The process of claim 1 further characterized in that said purifiedhydrogen stream is centrifugally compressed.

3. The process of claim 1 further characterized in that a reciprocatingcompressor raises the pressure of said puried hydrogen stream.

4. The process of claim 1 further characterized in that said secondhydrocarbonaceous charge stock comprises a mixture of natural gas and atleast a portion of said second vaporous phase.

5. The process of claim 1 further characterized in that saidhydroprocess is catalytic hydrocracking, and said conditions include atemperature of 400 F. to about 900 l5., a liquid hourly space velocityfrom 0.1 to 10.0 and hydrogen circulation of 1,000 to about 30,000s.c.f./bbl.

References Cited UNITED STATES PATENTS 3,551,106 12/1970 Smith et al.23-212 3,567,381 3/1971 Beavon et al 23-212 3,401,111 9/1968 Jackson208-108 2,750,261 6/1956 Ipatieff et al. 23-212 3,532,467 10/1970 Smithet al. 23-210 3,044,951 7/ 1962 Schlinger et al. 208-58 3,251,652 5/1966Pfeierle 23-213 DELBERT E. GANTZ, Primary Examiner G. E. SCHMITKONS,Assistant Examiner U.S. Cl. X.R.

